Most buildings put up before around 1920 were built with lime mortar. Lime is softer and more flexible than modern cement, and it lets moisture move out of the wall rather than trapping it inside.
The problem with cement on old brickwork
Cement mortar is harder than many older bricks. When a wall moves or gets wet, the stress goes into the bricks instead of the joints, and the faces of the bricks can crack and spall. Cement also holds moisture in, which can lead to damp.
Why lime works
- It is breathable, so moisture can escape
- It is flexible, so it moves with the building
- It is sacrificial, so the joints wear rather than the bricks
- It matches the original look of period brickwork
Is lime always the answer?
Not always. Newer buildings built with hard bricks and cement are usually best repointed to match. The right mortar depends on the building, so we always look at the existing masonry before specifying the mix.
